Abstract 641: Protein Disulfide Isomerase-A1 Overexpression Enhances Vascular Calcification in Mice

Abstract

Vascular calcification (VC) is an active pathophysiological process promoting enhanced morbidity and mortality without effective therapy. Oxidative stress and endoplasmic reticulum (ER) stress support cardiovascular calcification progression. We showed previously that the ER redox chaperone protein disulfide isomerase-A1 (PDI) is required for agonist-driven Nox NADPH oxidase activation. Oxidant levels and expression of Nox subunits and PDI are upregulated in calcifying rabbit valves. We hypothesized that PDI supports VC. We recently developed a new PDI overexpression mouse model (TgPDI) in FVB background (WT). To investigate whether TgPDI mice show increased VC, we challenged 20 week-old TgPDI mice with Vitamin-D 3 (VitD) for 14 days. Also, we incubated primary vascular smooth muscle cells (VSMC) isolated from WT or TgPDI mice with mineralizing medium (β-glycerophosphate 10mM + CaCl 2 6mM). TgPDI results were compared to those from respective WT littermates. We tested distinct VitD doses. At 9x10 4 IU/day, WT mice depicted negligible increases in calcification area (median 0.07% to 0.36% aorta cross-sectional area, p=ns, n=5), while TgPDI showed enhanced calcification (median 0.20 to 3.63 % area, p<0.05, n=4). The sum of calcification areas across all mice showed a 2.6-fold increase in TgPDI. TgPDI mice did not develop aortic valve stenosis or change in ascending aorta peak wave velocity at echocardiography. In vitro, VSMC phenotype marker expression (SM22 and alpha-actin) was enhanced in TgPDI vs. WT cells at baseline, while calcifying stimulation for 3 or 7 days decreased such VSMC marker expression both in WT and in TgPDI VSMC. Conversely, calcifying stimulation for 3 or 7 days showed no effects on ER stress marker expression (GRP78, GRP94). To assess whether these findings apply to humans, we examined femoral arteries from diabetic and non-diabetic patients with peripheral arterial disease, which showed increased arterial calcification and marked coincident PDI overexpression in samples from diabetic patients. In conclusion, PDI overexpression in vivo associates with enhanced VC after VitD calcifying stimulus. PDI and its associated signaling proteins deserve further study as potential therapeutic targets in VC progression.